Fluorinated ether composition, surface modifier, surfactant, liquid composition, and article

ABSTRACT

To provide a fluorinated ether composition capable of satisfying both high lubricity and high adhesive property, a lubricant, surface modifier or surfactant containing the fluorinated ether composition, and a liquid composition containing the fluorinated ether composition. The fluorinated ether composition comprises a fluorinated ether compound (A) represented by (X) n —Y A —(Z) m  and a fluorinated ether compound (B) represented by (X) s —Y B —(Z) t , wherein the content of the fluorinated ether compound (A) is from 15 to 80 mass % to the total amount of the fluorinated ether compound (A) and the fluorinated ether compound (B), and in the above formulae, X is HO—CH 2 —P 1 -[(C a F 2a O) b (CFQ 1 CF 2 O) c ]—, Z is R—P 2 —[(C d F 2d O) e (CFQ 2 CF 2 O) f ]—, n is 5 or 6, m is an integer of from 0 to 10, n+m is an integer of from 5 to 16, s is an integer of from 0 to 4, t is an integer of from 0 to 10, s+t is an integer of from 2 to 14, and each of Y A  and Y B  is a linking group.

TECHNICAL FIELD

The present invention relates to a fluorinated ether composition useful as a surface modifier, surfactant, etc.; a surface modifier or surfactant containing the fluorinated ether composition; a liquid composition comprising the fluorinated ether composition and a solvent; and an article having a film made of the fluorinated ether composition, on a substrate.

BACKGROUND ART

In a magnetic disk, a carbon protective film is formed on a magnetic recording layer for recording information, for the purpose of protecting a recorded information. Further, it is common to further form, thereon, a coating film (hereinafter referred to also as a “surface layer”) by applying a lubricant, for the purpose of protecting the magnetic disk and a reading head. As such a lubricant, a compound having a modified perfluoropolyether structure has heretofore been used.

Along with an increase in the recording capacity of a hard disk drive (hereinafter referred to also as “HDD”) in recent years, the distance between a magnetic disk as a recording medium and a reading head has been reduced so close as to bring them almost in contact each other. Further, the magnetic disk is rotated at a speed exceeding 10,000 rpm. Due to such a high rotational speed and closeness in distance between the magnetic disk and the reading head, the performance required for the surface layer has become higher. For example, in order to let the disk and the head be closer to each other, it becomes important to make the thickness of the surface layer to be thinner. Further, due to such closeness in distance, the frequency in contact increases, and therefore, a surface layer having higher lubricity is required. On the other hand, the surface layer is required to have higher adhesion to the magnetic disk so that the surface layer will not scatter from the top of the magnetic disk due to the high speed rotation.

However, in many cases, high lubricity and high adhesion are contradictory in nature to each other, and it is difficult to satisfy both at the same time.

For example, as a method to increase lubricity of the surface layer, there may, for example, be a method of using a lubricant which has a low molecular weight and a low viscosity, or a method of using a lubricant with low polarity which has no or little polar functional groups. However, in the case of using a lubricant which has a low molecular weight and a low viscosity, the vapor pressure is high, so that the lubricant tends to volatilize, and adhesion between the surface layer and the carbon protective layer tends to be low. Whereas, in the case of using a lubricant with low polarity, the polarity is low, so that its adhesion to the magnetic disk tends to be low, and the durability of the surface layer tends to be remarkably low, whereby the lubricant is likely to scatter due to rotation of the magnetic disk.

As a method to increase adhesion of the surface layer to the magnetic disk, there may be a method of using a lubricant which has a large content of polar functional groups. However, in the case of using such a lubricant, the viscosity of the surface layer tends to be high, and the lubricity tends to be remarkably low, whereby the magnetic disk is likely to be abraded.

To deal with such problems, e.g. Patent Documents 1 and 2 propose to use specific fluorinated ether compounds as lubricants. In Examples in Patent Document 1, a tri-functional fluorinated ether compound having three —CF₂CH₂OH terminals, and a hexa-functional fluorinated ether compound having three —CH₂CH(OH)CH₂OH terminals, are disclosed. In Patent Document 2, a di- to tetra-functional fluorinated ether compound having two, three or four —CF₂CH₂OH terminals, is disclosed.

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: WO2005/068534 -   Patent Document 2: WO2010/027096

DISCLOSURE OF INVENTION Technical Problem

According to the lubricants disclosed in Patent Documents 1 and 2, it is said to be possible to accomplish both high lubricity and high adhesion to a certain extent. However, there is still a room for improvement of such effects.

According to a study made by the present inventors, the di- to tetra-functional fluorinated ether compound having —CF₂CH₂OH terminals, is excellent in lubricity, but its adhesion cannot be said to be sufficient. The hexa-functional fluorinated ether compound having three —CH₂CH(OH)CH₂OH terminals, has a problem that the viscosity of the surface layer to be formed, tends to be high, whereby the lubricity tends to be low. Further, there is a problem that it is difficult to form a thin film of the surface layer.

The present invention has been made under these circumstances, and it is an object of the present invention to provide a fluorinated ether composition capable of satisfying both high lubricity and high adhesive property, and a surface modifier, surfactant, liquid composition and article using such a fluorinated ether composition.

Solution to Problem

The present invention provides a fluorinated ether composition, surface modifier, surfactant, liquid composition and article having the following constructions [1] to [15].

[1] A fluorinated ether composition comprising a fluorinated ether compound (A) represented by the following formula (A) and a fluorinated ether compound (B) represented by the following formula (B), wherein the content of the fluorinated ether compound (A) is from 15 to 80 mass % to the total amount of the fluorinated ether compound (A) and the fluorinated ether compound (B):

(X)_(n)—Y^(A)—(Z)_(m)  (A)

(X)_(s)—Y^(B)—(Z)_(t)  (B)

provided that the symbols in the formulae have the following meanings:

in the above formula (A), X is a group represented by the following formula (X), Z is a group represented by the following formula (Z), n is 5 or 6, m is an integer of from 0 to 10, n+m is an integer of from 5 to 16, and Y^(A) is a (n+m) valent linking group, and

in the above formula (B), X and Z have the same meanings as above, respectively, s is an integer of from 0 to 4, t is an integer of from 0 to 10, s+t is an integer of from 2 to 14, and Y^(B) is a (s+t) valent linking group:

HO—CH₂—P¹—[(C_(a)F_(2a)O)_(b)(CFQ¹CF₂O)_(c)]—  (X)

R—P²—[(C_(d)F_(2d)O)_(e)(CFQ²CF₂O)_(f)]—  (Z)

in the above formula (X), a is an integer of from 1 to 5, b is an integer of from 1 to 100, c is an integer of from 0 to 100, P¹ is a bivalent linking group containing neither hydroxy group nor alkoxy group, or a single bond, and Q¹ is a halogen atom other than a fluorine atom, a hydrogen atom, a monovalent hydrocarbon group, a fluoroalkyl group, or a fluoroalkyl group having an etheric oxygen atom inserted between carbon-carbon atoms, provided that when b is 2 or more, the plurality of a corresponding to b present in the same molecule may be the same or different from one another, when c is 2 or more, the plurality of Q¹ corresponding to c present in the same molecule may be the same or different from one another, and alignment sequence of b number of (C_(a)F_(2a)O) units and c number of (CFQ¹CF₂O) units in a molecule may be any sequence,

in the above formula (Z), d is an integer of from 1 to 5, e is an integer of from 1 to 100, f is an integer of from 0 to 100, P² is a bivalent linking group containing neither hydroxyl group nor alkoxy group, or a single bond, Q² is a halogen atom other than a fluorine atom, a hydrogen atom, a monovalent hydrocarbon group, a fluoroalkyl group, or a fluoroalkyl group having an etheric oxygen atom inserted between carbon-carbon atoms, and R is a hydrogen atom, a halogen atom, a monovalent hydrocarbon group, a fluoroalkyl group, or a fluoroalkyl group having an etheric oxygen atom inserted between carbon-carbon atoms, provided that when e is 2 or more, the plurality of d corresponding to e present in the same molecule may be the same or different from one another, when f is 2 or more, the plurality of Q² corresponding to f present in the same molecule may be the same or different from one another, and alignment sequence of e number of (C_(d)F_(2d)O) units and f number of (CFQ²CF₂O) units in a molecule may be any sequence.

[2] The fluorinated ether composition according to [1], wherein the number average molecular weight in total of the fluorinated ether compound (A) and the fluorinated ether compound (B) is from 500 to 50,000. [3] The fluorinated ether composition according to [1] or [2], wherein the fluorinated ether compound (A) has a number average molecular weight of from 2,000 to 50,000 and a molecular weight distribution (Mw/Mn) of from 1.00 to 1.65. [4] The fluorinated ether composition according to any one of [1] to [3], wherein the fluorinated ether compound (B) has a number average molecular weight of from 500 to 10,000 and a molecular weight distribution (Mw/Mn) of from 1.00 to 1.65. [5] The fluorinated ether composition according to any one of [1] to [4], wherein the fluorinated ether compound (A) is a compound of the above formula (A) wherein m is an integer of from 0 to 3, X is a group represented by the following formula (X-1), and Z is a group represented by the following formula (Z-1):

HO—CH₂—CF₂O—(CF₂CF₂O)_(b-1)—  (X-1)

R—O—(CF₂CF₂O)_(e)—  (Z-1)

provided that the symbols in the formulae have the following meanings:

in the above formula (X-1), b is an integer of from 1 to 100,

in the above formula (Z-1), e is an integer of from 1 to 100, and R is as defined above.

[6] The fluorinated ether composition according to [5], wherein the above Y^(A) is a perfluoro organic group obtained by perfluorinating a group with a structure having hydroxy groups removed from a penta- or hexa-polyhydric alcohol. [7] The fluorinated ether composition according to any one of [1] to [6], wherein the fluorinated ether compound (B) is a compound of the above formula (B) wherein s is 4, t is from 0 to 2, X is a group represented by the following formula (X-1), and Z is a group represented by the following formula (Z-1):

HO—CH₂—CF₂O—(CF₂CF₂O)_(b-1)—  (X-1)

R—O—(CF₂CF₂O)_(e)—  (Z-1)

provided that the symbols in the formulae have the following meanings:

in the above formula (X-1), b is an integer of from 1 to 100,

in the above formula (Z-1), e is an integer of from 1 to 100, and R is as defined above.

[8] The fluorinated ether composition according to [7], wherein the above Y^(B) is a perfluoro organic group obtained by perfluorinating a group with a structure having hydroxy groups removed from a tetra- to hexa-polyhydric alcohol. [9] A surface modifier or surfactant containing the fluorinated ether composition as defined in any one of [1] to [8]. [10] A lubricant for a magnetic recording medium, containing the fluorinated ether composition as defined in any one of [1] to [8]. [11] A liquid composition comprising the fluorinated ether composition as defined in any one of [1] to [8] and a liquid medium. [12] The liquid composition according to [11], wherein the concentration of the fluorinated ether composition is from 0.005 to 50 mass %. [13] The liquid composition according to [11] or [12], wherein the liquid medium is a fluorinated organic solvent selected from a fluoro-alkane, a fluoro-aromatic compound and a fluoro-alkyl ether. [14] A coating method which comprises applying the liquid composition as defined in any one of [11] to [13] to a substrate surface and then, removing the liquid medium to form a film made of the fluorinated ether composition on the substrate surface. [15] An article having a film made of the fluorinated ether composition as defined in any one of [1] to [8], on a substrate.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a fluorinated ether composition capable of satisfying both high lubricity and high adhesive property, and a surface modifier, surfactant, liquid composition and article using such a fluorinated ether composition.

DESCRIPTION OF EMBODIMENTS

In this specification, a compound represented by the formula (A) may be referred to as a compound (A). Compounds represented by other formulae may be referred to in the same manner.

In this specification, a group represented by the formula (X) may be referred to as a group (X). Groups represented by other formulae may be referred to in the same manner.

In the present invention, “a fluorinated ether composition” is a composition composed of at least two fluorinated ether compounds. Composed of fluorinated ether compounds means containing no components other than fluorinated ether compounds except for inevitable impurities.

In the present invention, “a fluorinated ether compound” is an ether compound having a poly(oxyperfluoroalkylene) chain.

In the present invention, “a fluoroalkyl group” is a group having some or all of hydrogen atoms in an alkyl group substituted by fluorine atoms, and “a perfluoroalkyl group” is a group having all of hydrogen atoms in an alkyl group substituted by fluorine atoms.

In the present invention, “a fluoroalkylene group” is a group having some or all of hydrogen atoms in an alkylene group substituted by fluorine atoms, and “a perfluoroalkylene group” is a group having all of hydrogen atoms in an alkylene group substituted by fluorine atoms.

In the present invention, a number average molecular weight and a molecular weight distribution are values to be measured by gel permeation chromatography. As measuring conditions, it is possible to employ the conditions described in Examples given hereinafter.

[Fluorinated Ether Composition]

The fluorinated ether composition of the present invention is characterized by comprising a fluorinated ether compound (A) (hereinafter referred to also as a “compound (A)”) and a fluorinated ether compound (B) represented by the following formula (B) (hereinafter referred to also as a “compound (B)”), wherein the content of the compound (A) is from 15 to 80 mass % to the total amount of the compound (A) and the compound (B).

(Compound (A))

The compound (A) is a compound having n monovalent groups (X) and m monovalent groups (Z) bonded to Y^(A).

(X)_(n)—Y^(A)—(Z)_(m)  (A)

In the formula (A), X is a group represented by the following formula (X).

HO—CH₂—P¹-[(C_(a)F_(2a)O)_(b)(CFQ¹CF₂O)_(c)]—  (X)

In the formula (X), a is an integer of from 1 to 5, preferably an integer of from 2 to 4, particularly preferably 2. When a is an integer of from 3 to 5, C_(a)F_(2a) may have a linear chain structure or a branched chain structure.

b represents the number of (C_(a)F_(2a)O) units and is an integer of from 1 to 100, preferably an integer of from 5 to 50, particularly preferably an integer of from 5 to 30.

c represents the number of (CFQ¹CF₂O) units and is an integer of from 0 to 100, preferably an integer of from 0 to 50, particularly preferably from 0 to 10.

When b is 2 or more, the plurality of a corresponding to b present in the same molecule may be the same or different from one another. That is, b number of (C_(a)F_(2a)O) units may be the same or different from one another.

When c is 2 or more, the plurality of Q¹ corresponding to c present in the same molecule may be the same or different from one another. That is, c number of (CFQ¹CF₂O) units may be the same or different from one another.

When b+c is 2 or more, alignment sequence of b number of (C_(a)F_(2a)O) units and c number of (CFQ¹CF₂O) units in —[(C_(a)F_(2a)O)_(b)(CFQ¹CF₂O)_(c)]— in a molecule may be any sequence.

For example, in a case where each of unit (C_(a)F_(2a)O) and unit (CFQ¹CF₂O) is present in a single unit, the unit bonded to HO—CH₂—P¹— may be the (C_(a)F_(2a)O) unit or the (CFQ¹CF₂O) unit.

In a case where unit (C_(a)F_(2a)O) and unit (CFQ¹CF₂O) are present, and at least either one of them is present in two or more units, alignment sequence of these units may be in a block form or a random form.

In the formula (X), P¹ is a bivalent linking group containing neither hydroxy group nor alkoxy group, or a single bond.

The bivalent linking group containing neither hydroxy group nor alkoxy group, is preferably a bivalent organic group containing neither hydroxy group nor alkoxy group, and specific examples may be an alkylene group, an alkylene group having an etheric oxygen atom inserted between carbon-carbon atoms, a fluoro-alkylene group, a fluoro-alkylene group having an etheric oxygen atom inserted between carbon-carbon atoms, one having a hetero atom such as phosphazene, an unsaturated hydrocarbon group, etc.

As P¹, a single bond is preferred.

In the formula (X), Q¹ is a halogen atom other than a fluorine atom, a hydrogen atom, a monovalent hydrocarbon group, a fluoroalkyl group, or a fluoroalkyl group having an etheric oxygen atom inserted between carbon-carbon atoms.

The halogen atom other than a fluorine atom may, for example, be a chlorine atom, an iodine atom or a bromine atom, and from the viewpoint of the production efficiency, a chlorine atom is preferred.

The monovalent hydrocarbon group may be saturated or unsaturated and is preferably a saturated hydrocarbon group (an alkyl group). The structure of the hydrocarbon group may be any of a linear chain structure, a branched chain structure, a ring structure or a structure having a partially ring structure, preferably a linear chain structure or a branched chain structure, particularly preferably a linear chain structure. The number of carbon atoms in the hydrocarbon group is preferably from 1 to 10.

The fluoroalkyl group may be a fluoroalkyl group having some of hydrogen atoms in an alkyl group substituted by fluorine atoms, or a perfluoroalkyl group. The number of carbon atoms in the fluoroalkyl group is preferably from 1 to 100, particularly preferably from 1 to 20.

The fluoroalkyl group having an etheric oxygen atom inserted between carbon-carbon atoms, may be a fluoroalkyl group having some of hydrogen atoms in an alkyl group substituted by fluorine atoms, or a perfluoroalkyl group. The number of carbon atoms in the fluoroalkyl group is preferably from 2 to 100, particularly preferably from 2 to 20.

The following group (Q−1) may, for example, be mentioned as a specific example of the fluoroalkyl group having an etheric oxygen atom inserted between carbon-carbon atoms.

R¹—(OC_(h)F_(2h))_(j)—  (Q-1)

In the formula, R¹ is a fluoroalkyl group, h is an integer of from 1 to 5, and j is from 1 to 100 and is an integer whereby the number of carbon atoms in the entire group (Q-1) becomes at most 100.

When h is an integer of from 3 to 5, C_(h)F_(2h) may have a linear chain structure or a branched chain structure.

R¹ may be a fluoroalkyl group having some of hydrogen atoms in an alkyl group substituted by fluorine atoms, or a perfluoroalkyl group. The number of carbon atoms in the fluoroalkyl group is at least 1 and an integer whereby the number of carbon atoms in the entire group (Q-1) becomes at most 100, and it is preferably from 1 to 6.

The group (X) is preferably a group of the formula (X) wherein a is 2 (provided that only in (C_(a)F_(2a)O) bonded to P¹, a is 1), b is an integer of from 1 to 100, c is from 0 to 10, and P¹ is a single bond or —CH₂OCH₂—.

The group (X) is more preferably the following group (X-1) or (X-2).

HO—CH₂—CF₂O—(CF₂CF₂O)_(b-1)—  (X-1)

HO—CH₂—CH₂OCH₂—CF₂O—(CF₂CF₂O)_(b-1)—  (X-2)

In the formulae (X-1) and (X-2), b is an integer of from 1 to 100, preferably an integer of from 5 to 50, particularly preferably an integer of from 5 to 30.

Among them, particularly preferred as the group (X) is the group (X-1), whereby the production will be easy, and the compound will be stable and scarcely decomposable.

In the formula (A), Z is a group represented by the following formula (Z).

R—P²—[(C_(d)F_(2d)O)_(e)(CFQ²CF₂O)_(f)]—  (Z)

In the formula (Z), d is an integer of from 1 to 5, preferably an integer of from 2 to 4, particularly preferably 2. When d is an integer of from 3 to 5, C_(d)F_(2d) may have a linear chain structure or a branched chain structure.

e represents the number of (C_(d)F_(2d)O) units and is an integer of from 1 to 100, preferably an integer of from 5 to 50, particularly preferably an integer of from 5 to 30.

f represents the number of (CFQ²CF₂O) units and is an integer of from 0 to 100, preferably an integer of from 0 to 50, particularly preferably from 0 to 10.

When e is 2 or more, the plurality of d corresponding to e present in the same molecule may be the same or different from one another. That is, e number of (C_(d)F_(2d)O) units may be the same or different from one another.

When f is 2 or more, the plurality of Q² corresponding to f present in the same molecule may be the same or different from one another. That is, f number of (CFQ²CF₂O) units may be the same or different from one another.

When e+f is 2 or more, alignment sequence of e number of (C_(d)F_(2d)O) units and f number of (CFQ²CF₂O) units in —[(C_(d)F_(2d)O)_(e)(CFQ²CF₂O)_(f)]— in a molecule may be any sequence.

For example, in a case where each of unit (C_(d)F_(2d)O) and unit (CFQ²CF₂O) is present in a single unit, the unit bonded to R—P²— may be the (C_(d)F_(2d)O) unit or the (CFQ²CF₂O) unit.

In a case where unit (C_(d)F_(2d)O) and unit (CFQ²CF₂O) are present, and at least either one of them is present in two or more units, alignment sequence of these units may be in a block form or a random form.

In the formula (Z), P² is a bivalent linking group containing neither hydroxyl group nor alkoxy group, or a single bond.

The bivalent linking group containing neither hydroxyl group nor alkoxy group, may, for example, be a bivalent organic group containing neither hydroxyl group nor alkoxy group, or —O—.

P² is preferably —O—.

In the formula (Z), Q² is a halogen atom other than a fluorine atom, a hydrogen atom, a monovalent hydrocarbon group, a fluoroalkyl group, or a fluoroalkyl group having an etheric oxygen atom inserted between carbon-carbon atoms.

The halogen atom other than a fluorine atom, the monovalent hydrocarbon group, the fluoroalkyl group, and the fluoroalkyl group having an etheric oxygen atom inserted between carbon-carbon atoms, may, respectively, be the same ones as mentioned above for Q¹.

In the formula (Z), R is a hydrogen atom, a halogen atom, a monovalent hydrocarbon group, a fluoroalkyl group, or a fluoroalkyl group having an etheric oxygen atom inserted between carbon-carbon atoms.

The halogen atom may, for example, be a fluorine atom, a chlorine atom, an iodine atom or a bromine atom, and is preferably a fluorine atom.

The monovalent hydrocarbon group may be saturated or unsaturated, and is preferably a saturated hydrocarbon group (an alkyl group). The structure of the hydrocarbon group may be any of a linear chain structure, a branched chain structure, a ring structure, or a structure having a partially ring structure, and is preferably a linear chain structure or a branched chain structure, particularly preferably a linear chain structure. The number of carbon atoms in the hydrocarbon group is preferably from 1 to 20. As the hydrocarbon group, an alkyl group is preferred.

The fluoroalkyl group may be a fluoroalkyl group having some of hydrogen atoms in an alkyl group substituted by fluorine atoms, or a perfluoroalkyl group. The structure of the fluoroalkyl group may be any of a linear chain structure, a branched chain structure, a ring structure and a structure having a partially ring structure, and is preferably a linear chain structure or a branched chain structure, particularly preferably a linear chain structure. The number of carbon atoms in the fluoroalkyl group is preferably from 1 to 100, particularly preferably from 1 to 10.

The fluoroalkyl group in the fluoroalkyl group having an etheric oxygen atom inserted between carbon-carbon atoms may be a fluoroalkyl group having some of hydrogen atoms in an alkyl group substituted by fluorine atoms, or a perfluoroalkyl group. The number of carbon atoms in the fluoroalkyl group is preferably from 2 to 100, particularly preferably from 2 to 10.

The following groups (R-1) to (R-4) may, for example, be mentioned as specific examples of R.

CF₃(CF₂)_(p)—  (R-1)

CF₃CF(CF₃)—  (R-2)

C_(y) ^(F)—(CF₂)_(q)—  (R-3)

A_(d) ^(F)-(CF₂)_(r)—  (R-4)

Here, p is an integer of from 0 to 15 (preferably an integer of from 0 to 9), C_(y) ^(F) is a perfluorocyclohexyl group, q is an integer of from 0 to 15, A_(d) ^(F) is a perfluoroadamantyl group, and r is an integer of from 0 to 15.

In the formula (Z), it is preferred that d is 2, e is an integer of from 1 to 100, f is from 0 to 10, and P² is —O—. That is, the group (Z) is preferably the following group (Z-1).

R—O—(CF₂CF₂O)_(e)—  (Z-1)

In the formula (Z-1), e is an integer of from 1 to 100, preferably an integer of from 5 to 50, particularly preferably an integer of from 5 to 30.

R is as defined above, preferably any one of groups (R-1) to (R-4), particularly preferably group (R-1).

The group (Z-1) is particularly preferably any one of the following groups (Z-11) to (Z-14).

CF₃—O—(CF₂CF₂O)_(g)-  (Z-11)

CF₃CF₂—O—(CF₂CF₂O)_(g)-  (Z-12)

CF₃(CF₂)₂—O—(CF₂CF₂O)_(g)-  (Z-13)

CF₃(CF₂)₅—O—(CF₂CF₂O)_(g)—  (Z-14)

In the formula (A), n is 5 or 6.

m is an integer of from 0 to 10, preferably an integer of from 0 to 3, particularly preferably 0 or 1.

n+m is an integer of from 5 to 16, preferably an integer of from 5 to 9, particularly preferably an integer of from 5 to 7. When n+m (valence of Y^(A)) is within the above range, the adhesion to a substrate will be excellent.

In the compound (A), n groups (X) may be the same or different from one another. When m is 2 or more, m groups (Z) in the compound (A) may be the same or different from one another.

In the formula (A), Y^(A) is a (n+m) valent linking group.

Y^(A) may, for example, be a (n+m) valent fluoro-saturated hydrocarbon group, a (n+m) valent fluoro-saturated hydrocarbon group having an etheric oxygen atom inserted between carbon-carbon atoms, or a (n+m) valent cyclophosphazene group. Among them, preferred is a (n+m) valent fluoro-saturated hydrocarbon group, or a (n+m) valent fluoro-saturated hydrocarbon group having an etheric oxygen atom inserted between carbon-carbon atoms.

The fluoro-saturated hydrocarbon group may be a fluoro-saturated hydrocarbon group having some of hydrogen atoms in an alkyl group substituted by fluorine atoms, or a perfluoro-saturated hydrocarbon group, and is preferably a perfluoro-saturated hydrocarbon group. The structure of the perfluoro-saturated hydrocarbon group may be any of a branched chain structure, a ring structure or a structure having a partially ring structure, and is preferably a branched chain structure. The number of carbon atoms in the perfluoro-saturated hydrocarbon group is preferably from 2 to 50, more preferably from 2 to 20, particularly preferably from 5 to 20.

The perfluoro-saturated hydrocarbon group in a perfluoro-saturated hydrocarbon group having an etheric oxygen atom inserted between carbon-carbon atoms, may be the same as mentioned above. The number of etheric oxygen atoms in the perfluoro-saturated hydrocarbon group having an etheric oxygen atom inserted between carbon-carbon atoms, is not particularly limited, but is preferably from 1 to 3.

Here, the etheric oxygen atom is present between carbon-carbon atoms, and therefore, no etheric oxygen atom is present at a terminal portion of Y^(A) bonded to each of group (X) and group (Z).

From the viewpoint of stability of the compound (A), it is preferred that no —OCF₂O— structure is present in the compound (A). Accordingly, in a case where Y^(A) is a (n+m) valent fluoro-saturated hydrocarbon group, or a (n+m) valent fluoro-saturated hydrocarbon group having an etheric oxygen atom inserted between carbon-carbon atoms, it is preferred that no —OCF₂O— structure is present in Y^(A).

Here, “no —OCF₂O— structure is present” means that the presence of such a structure cannot be detected by a usual analytical method (such as ¹⁹F-NMR).

Specific examples of Y^(A) may, for example, be a group obtained by fluorinating a group of a structure having hydroxy groups removed from a (n+m) valent polyhydric alcohol, a group of a structure having substituents bonded to phosphorus atoms removed from a cyclophosphazene compound, etc.

The (n+m) valent polyhydric alcohol may have an etheric oxygen atom. As the group obtained by fluorinating a group of a structure having hydroxy groups removed from a (n+m) valent polyhydric alcohol, a perfluoro-organic group is preferred.

The (n+m) valent polyhydric alcohol may, for example, be a sugar alcohol such as glucose, dipentaerythritol or sorbitol.

The following groups (Y5-1), (Y6-1), etc. may be mentioned as specific examples of the group obtained by fluorinating a group of a structure having hydroxy groups removed from a (n+m) valent polyhydric alcohol.

The following groups (Y6-2), etc. may be mentioned as specific examples of the group of a structure having substituents bonded to phosphorus atoms removed from a cyclophosphazene compound.

The compound (A) is preferably a compound of the formula (A) wherein m is an integer of from 0 to 3, X is group (X-1) and Z is group (Z-1), i.e. the following compound (A-1).

HO—CH₂—CF₂O—(CF₂CF₂O)_(b-1)-  (X-1)

R—O—(CF₂CF₂O)_(e)-  (Z-1)

In the formula (X-1), b is an integer of from 1 to 100, preferably an integer of from 5 to 50, particularly preferably an integer of from 5 to 30.

In the formula (Z-1), e is an integer of from 1 to 100, preferably an integer of from 5 to 50, particularly preferably an integer of from 5 to 30.

R is as defined above.

(X¹)_(n)—Y^(A1)—(Z¹)_(m1)  (A-1)

In the formula (A-1), X¹ is group (X-1), Z¹ is group (Z-1), n is as defined above, m1 is an integer of from 0 to 3 (preferably 0 or 1), and Y^(A1) is a (n+m1) valent linking group.

In the formula, n groups (X-1) may be the same or different from one another. When m1 is 2 or more, m1 groups (Z-1) in the formula may be the same or different from one another.

The (n+m1) valent linking group for Y^(A1) may be the same one as mentioned above for Y^(A).

As the compound (A-1), the following compounds (A-11) to (A-14), etc. are preferred.

(X¹)₅—Y⁵  (A-11)

(X¹)₅—Y⁶—Z¹  (A-12)

(X¹)₆—Y⁶  (A-13)

(X¹)₆—Y⁷—Z¹  (A-14)

In the formulae, X¹ and Z¹ are, respectively, as defined above, and their preferred ranges are also the same. Y⁵ is a penta-valent linking group, Y⁶ is a hexa-valent linking group, and Y⁷ is a hepta-valent linking group.

Each of Y⁵, Y⁶ and Y⁷ may be the same as the penta-, hexa- or hepta-valent one among the linking groups mentioned above for Y^(A). As a specific example of the penta-valent linking group, group (Y5-1) may, for example, be mentioned. As a specific example of the hexa-valent linking group, group (Y6-1) or group (Y6-2) may, for example, be mentioned.

The number average molecular weight (Mn) of the compound (A) is preferably from 500 to 50,000, particularly preferably from 2,000 to 20,000.

The molecular weight distribution (Mw/Mn) of the compound (A) is preferably from 1.00 to 1.65, particularly preferably from 1.00 to 1.50.

When the number average molecular weight and the molecular weight distribution are within the above ranges, the adhesion to a substrate and the durability will be excellent, and the volatility will be low.

The compound (A) contained in the fluorinated ether composition of the present invention may be one type alone, or two or more types in combination.

The content of the compound (A) in the fluorinated ether composition of the present is from 15 to 80 mass %, preferably from 40 to 60 mass %, to the total amount of the compound (A) and the compound (B). When the content is at least the lower limit value in the above range, the fluorinated ether composition of the present invention will be excellent in adhesion to e.g. a magnetic disk. When the content is at most the upper limit value in the above range, the ratio of the compound (B) will be high, so that the fluorinated ether composition of the present invention will be excellent in lubricity.

(Compound (B))

The compound (B) is a compound having s monovalent groups (X) and t monovalent groups (Z) bonded to Y^(B).

(X)_(s)—Y^(B)—(Z)_(t)  (B)

Group (X) and group (Z) are, respectively, the same as group (X) and group (Z) mentioned above in the description of the compound (A).

Group (X) and group (Z) in the compound (B) may, respectively, be the same or different from group (X) and group (Z) in the compound (A).

In the formula (B), s is an integer of from 0 to 4, preferably an integer of from 2 to 4, particularly preferably 3 or 4.

t is an integer of from 0 to 10, preferably from 0 to 3.

s+t is an integer of from 2 to 14, preferably an integer of from 2 to 10, particularly preferably an integer of from 3 to 6. When s+t (valence of Y^(B)) is within the above range, the production will be easy, the boiling point will be suitable, and the lubricity will be excellent.

When s is 2 or more, s groups (X) in the compound (B) may be the same or different from one another. When t is 2 or more, t groups (Z) in the compound (B) may be the same or different from one another.

Y^(B) is a (s+t) valent linking group.

Y^(B) may, for example, be a (s+t) valent fluoro-saturated hydrocarbon group, a (s+t) valent fluoro-saturated hydrocarbon group having an etheric oxygen atom inserted between carbon-carbon atoms, or a (s+t) valent cyclophosphazene group. Among them, preferred is a (s+t) valent fluoro-saturated hydrocarbon group, or a (s+t) valent fluoro-saturated hydrocarbon group having an etheric oxygen atom inserted between carbon-carbon atoms.

The fluoro-saturated hydrocarbon group may be a fluoro-saturated hydrocarbon group having some of hydrogen atoms in an alkyl group substituted by fluorine atoms, or a perfluoro-saturated hydrocarbon group, and is preferably a perfluoro-saturated hydrocarbon group. The structure of the perfluoro-saturated hydrocarbon group may be any of a branched chain structure, a ring structure or a structure having a partially ring structure, and is preferably a branched chain structure. The number of carbon atoms in the perfluoro-saturated hydrocarbon group is preferably from 2 to 50, more preferably from 2 to 20, particularly preferably from 5 to 20.

The perfluoro-saturated hydrocarbon group in a perfluoro-saturated hydrocarbon group having an etheric oxygen atom inserted between carbon-carbon atoms, may be the same as mentioned above. The number of etheric oxygen atoms in the perfluoro-saturated hydrocarbon group having an etheric oxygen atom inserted between carbon-carbon atoms, is not particularly limited, but is preferably from 1 to 3.

Here, the etheric oxygen atom is present between carbon-carbon atoms, and therefore, no etheric oxygen atom is present at a terminal portion of Y^(B) bonded to each of group (X) and group (Z).

From the viewpoint of stability of the compound (B), it is preferred that no —OCF₂O— structure is present in the compound (B). Accordingly, in a case where Y^(B) is a (s+t) valent fluoro-saturated hydrocarbon group, or a (s+t) valent fluoro-saturated hydrocarbon group having an etheric oxygen atom inserted between carbon-carbon atoms, it is preferred that no —OCF₂O— structure is present in Y^(B).

In a case where Y^(B) is a trivalent linking group, Y^(B) is preferably a perfluoroalkane-triyl group. The number of carbon atoms in the perfluoroalkane-triyl group is preferably from 1 to 20, particularly preferably from 3 to 5. For example, a perfluoro-organic group obtained by perfluorinating a group of a structure having hydroxy groups removed from a trihydric alcohol such as glycerol, may be mentioned.

The following groups (Y3-1) to (Y3-3), etc. may be mentioned as specific examples of the trivalent linking group. In the formulae (Y3-2) and (Y3-3), k is an integer of from 1 to 10, and 3 k present in the same molecule may be the same or different from one another.

In a case where Y^(B) is a tetravalent linking group, Y^(B) is preferably a perfluoroalkane-tetrayl group, or a perfluoroalkane-tetrayl group having an etheric oxygen atom inserted between carbon-carbon atoms. The number of carbon atoms in the perfluoroalkane-tetrayl group is preferably from 1 to 20, particularly preferably from 3 to 5. For example, a perfluoro-organic group obtained by perfluorinating a group of a structure having hydroxy groups removed from a tetrahydric alcohol such as erythritol, pentaerythritol or diglycerol, may be mentioned.

The following groups (Y4-1) to (Y4-3), etc. may be mentioned as specific examples of the tetravalent linking group.

In a case where Y^(B) is a penta-valent linking group, the above group (Y5-1) may be mentioned as a specific example of such a linking group.

In a case where Y^(B) is a hexa-valent linking group, the above group (Y6-1) or group (Y6-2) may be mentioned as a specific example of such a linking group.

The compound (B) is preferably a compound of the formula (B) wherein s is 4, X is group (X-1) and Z is group (Z-1), i.e. the following compound (B-1).

HO—CH₂—CF₂O—(CF₂CF₂O)_(b-1)—  (X-1)

R—O—(CF₂CF₂O)_(e)—  (Z-1)

Group (X-1) and group (Z-1) are, respectively, the same as group (X-1) and group (Z-1) in the above compound (A-1).

Group (X-1) and group (Z-1) in the compound (B-1) may, respectively, be the same as or different from group (X-1) and group (Z-1) in the above compound (A-1).

(X¹)₄—Y^(B1)—(Z¹)_(t)  (B-1)

In the formula (B-1), X¹ is group (X-1), Z¹ is group (Z-1), t is as defined above, and Y^(B1) is a (4+t) valent linking group. In the formula (B-1), t is preferably from 0 to 2.

In the formula, 4 groups (X-1) may be the same or different from one another. When t is 2 or more, t groups (Z-1) in the formula may be the same or different from one another.

The (4+t) valent linking group for Y^(B1) may be the same one as mentioned above for Y^(B). Particularly preferred is the above-mentioned perfluoro-organic group obtained by fluorinating a group of a structure having hydroxy groups removed from a tetra- to hexa-polyhydric alcohol.

As the compound (B-1), the following compounds (B-11) and (B-12) are preferred.

(X¹)₄—Y⁴  (B-11)

(X¹)₄—Y⁵—Z¹  (B-12)

In the formulae, X¹ and Z¹ are, respectively, as defined above, Y⁴ is a tetra-valent linking group, and Y⁵ is a penta-valent linking group.

Each of Y⁴ and Y⁵ may be the same one as the tetra- or penta-valent linking group mentioned above for Y^(B).

The number average molecular weight (Mn) of the compound (B) is preferably from 500 to 10,000, particularly preferably from 1,000 to 10,000.

The molecular weight distribution (Mw/Mn) of the compound (B) is preferably from 1.00 to 1.65, particularly preferably from 1.00 to 1.50.

When the number average molecular weight and the molecular weight distribution are within the above ranges, the adhesion to a substrate will be excellent, and the volatility will be low.

The compound (B) contained in the fluorinated ether composition of the present invention may be one type alone, or two or more types in combination.

The content of the compound (B) in the fluorinated ether composition of the present invention is from 20 to 85 mass %, preferably from 40 to 60 mass %, to the total amount of the compound (A) and the compound (B).

The total content of the compound (A) and the compound (B) in the fluorinated ether composition of the present invention is preferably from 80 to 100 mass %, more preferably from 90 to 100 mass %, particularly preferably 100 mass %, to the total mass of the fluorinated ether composition. When the total content of the compound (A) and the compound (B) is at least the above lower limit value, the fluorinated ether composition of the present invention will be excellent in adhesion to a substrate and in lubricity.

In the fluorinated ether composition of the present invention, the number average molecular weight in total of the compound (A) and the compound (B) is preferably from 500 to 50,000, particularly preferably from 1,000 to 20,000. When the number average molecular weight in such total is within the above range, the adhesion to a substrate and the lubricity will be excellent, the volatility will be low, and the durability for a long period of time will be excellent.

The number average molecular weight in such total can be confirmed by mixing the compound (A) and the compound (B) at the content ratio between the compound (A) and the compound (B) in the fluorinated ether composition, and measuring the number average molecular weight with respect to the obtained mixture. In a case where a fluorinated ether composition is composed of the compound (A) and the compound (B), the number average molecular weight in such total is the same as the number average molecular weight which is measured with respect to the fluorinated ether composition.

(Another Fluorinated Ether Compound)

The fluorinated ether composition of the present invention may be one composed of the compound (A) and the compound (B), or may further contain another fluorinated ether compound (hereinafter referred to also as “compound (C)”) other than the compound (A) and the compound (B).

As the compound (C), it is possible to use a conventional one known as a fluorinated ether compound which may be used as e.g. a lubricant. For example, FONBLIN ZTETRAOL (manufactured by Solvay), A-20H (manufactured by MORESCO), etc. may be mentioned.

(Method for Producing Fluorinated Ether Composition)

The fluorinated ether composition of the present invention may be produced, for example, by mixing the compound (A) and the compound (B) (and, as the case requires, the compound (C)) at a prescribed mass ratio.

As the compound (A) and the compound (B), the respective commercial products may be used, or ones produced by using known production methods may be used.

A method for producing the compound (A) will be described below. The compound (B) may be produced by the same production method except that the raw materials for the production are changed to raw materials having chemical structures corresponding to the compound (B).

(Method for Producing Compound (A))

The compound (A) may be produced, for example, by changing the raw materials for the production in the method disclosed in e.g. WO 2005/068534 or WO 2010/027096 to raw materials having chemical structures corresponding to the compound (A).

For example, a compound wherein Y^(A) is a (n+m) valent perfluoro-saturated hydrocarbon group, or a (n+m) valent perfluoro-saturated hydrocarbon group having an etheric oxygen atom inserted between carbon-carbon atoms, may be produced in the same manner as the method for obtaining compound (A-4) as disclosed in WO 2005/068534. Specifically, it may be produced by subjecting an ethylene oxide adduct of a polyhydric alcohol to esterification, liquid phase fluorination and ester-decomposition reaction to obtain a compound having COF at its terminal, and subjecting the compound to treatment by the following method 1-1 or 1-2.

(Method 1-1) A method of reacting the compound having COF at its terminal with an alcohol or water to convert the terminal to an ester or carboxylic acid, followed by reduction.

(Method 1-2) A method of subjecting the compound having COF at its terminal to ester-exchange with an alcohol to have the terminal esterified, followed by reduction.

Among them, in the present invention, it is preferred to adopt the method by ester exchange as disclosed in method 1-2, from the viewpoint of production efficiency.

In the above methods, in a case where the ethylene oxide adduct of a polyhydric alcohol as the starting material, has non-fluorinated group (Z) in addition to ethylene oxide-added hydroxy groups, a compound having group (X) and group (Z) in combination will be obtained.

Even if the ethylene oxide adduct of a polyhydric alcohol as the starting material, does not have non-fluorinated group (Z), if the liquid phase fluorination reaction conditions are severe, there may be a case where a terminal breakage reaction of molecules will take place to produce, as a byproduct, a compound having group (X) and group (Z) in combination.

As the ethylene oxide adduct of a polyhydric alcohol as the starting material, compounds having various structures and molecular weights are inexpensively and readily commercially available.

If the fluorine gas concentration in the liquid phase fluorination reaction becomes high, the proportion for forming group (Z) tends to be high. In a case where it is desired to suppress formation of the compound having group (Z), the fluorine gas concentration is preferably from 5.0 to 50 vol %, particularly preferably from 10 to 30 vol %.

The product formed by the reaction may be subjected to a purification step, as the case requires, to preferably remove unnecessary compounds by the purification. The purification method may, for example, be a method for removing metal impurities, anionic impurities, etc. by an ion-adsorbing polymer, a supercritical fluid extraction method, or a column chromatography method. It is preferred to use these methods in combination.

Advantageous Effects

The compound (A) is a penta- or hexa-functional compound having 5 or 6 hydroxy groups derived from group (X), and it is poor in lubricity, but is excellent in adhesion to e.g. a magnetic disk. The compound (B) is a zero- to tetra-functional compound having 0 to 4 hydroxy groups derived from group (X), and it is poor in adhesion, but is excellent in lubricity. The fluorinated ether composition of the present invention comprises the compound (A) and the compound (B) in such a ratio that the content of the compound (A) is from 15 to 80 mass % to the total amount of the compound (A) and the compound (B), whereby it is possible to attain both of excellent adhesion of the compound (A) and excellent lubricity of the compound (B).

Accordingly, by forming a coating film (surface layer) containing the fluorinated ether composition of the present invention on a substrate of a magnetic disk, it is possible to impart excellent lubricity and excellent durability. For example, by forming a surface layer containing the fluorinated ether composition of the present invention as a lubricant on a carbon protective film of a magnetic disk, it is possible to impart lubricity capable of sufficiently protecting the magnetic disk and a reading head even if the frequency in contact is increased by closeness in distance between the magnetic disk and the reading head. Further, a trouble of decrease or disappearance of the lubricity due to vaporization of the lubricant during rotation of the magnetic disk or due to scattering of the lubricant at the time of increasing the rotational speed of the magnetic disk (e.g. to a level exceeding 10,000 rpm) will be less likely to occur.

Further, according to the fluorinated ether composition of the present invention, it becomes easy to form a surface layer of a thin film (e.g. a film thickness of at most 1 nm).

This is considered to be attributable to that hydroxy groups in the compound (A) or (B), particularly in the compound (A), are derived from group (X). That is, as the hydroxy groups are derived from group (X), the length per one branched chain is short as compared with a case where, like the hexa-functional fluorinated ether compound disclosed in Patent Document 1, the compound has three —CH₂CH(OH)CH₂OH terminals. (For example, in a case where the compound (A) has 6 hydroxy groups and has the same number average molecular weight as such a compound, since such a compound has 2 hydroxy groups at a —CH₂CH(OH)CH₂OH terminal, the length of the group having such a terminal will be twice.) It is considered that since the distance between the hydroxy group terminals becomes short, the height of molecules on the substrate will be low when all hydroxy groups are bonded onto the substrate.

(Uses)

The fluorinated ether composition of the present invention is useful as a surface modifier or a surfactant. As the surface modifier, a lubricant may, for example, be mentioned.

The fluorinated ether composition of the present invention is useful also for other uses than above. Other uses may, for example, be a wire coating material, an ink repellent (e.g. for coating, or for a printing machine such as an ink jet), an adhesive for semiconductors (such as an adhesive for LOC (lead on chip) tapes, a protective coating for semiconductors (such as a moisture-proof coating agent, or a flux creeping-up preventive agent for a solder), an additive to a thin film to be used in the optical field (such as a pellicle film), a lubricant for an anti-reflection film for display, or an anti-reflection film for a resist), etc.

The fluorinated ether composition of the present invention is useful for an application wherein a coating film (surface layer) containing the fluorinated ether composition is formed on a substrate.

The surface layer containing the fluorinated ether composition of the present invention contains a fluorinated ether compound (such as compound (A)) having —CH₂—OH at its molecular terminals and thus maintains high lubricity. Therefore, by forming such a surface layer on a substrate, it is possible to impart a function such as lubricity. Further, the formed surface layer has high adhesion to the substrate and is excellent in durability.

Further, such a surface layer is transparent and has a low refractive index, or is excellent in heat resistance or chemical resistance.

The shape and material of the substrate on which the surface layer is to be formed, are not particularly limited, and may be ones suitable for the application of the substrate provided with such a surface layer. The application of the substrate provided with such a surface layer, may, for example, be a magnetic disk, an optical fiber, a mirror, a solar cell, an optical disk, a touch panel, an exposure and fixing drum, a film condenser, various films such as an antireflection film for glass windows, etc.

From the viewpoint of usefulness of the present invention, a magnetic disk is preferred as the substrate. The magnetic disk may, for example, be one having a primer layer, a recording layer and a diamond-like carbon protective film (DLC film) formed sequentially on a NiP-plated substrate (such as aluminum or glass). The thickness of the DLC film is preferably at most 5.0 nm. The average surface roughness (Ra) of the DLC film is preferably at most 2.0 nm.

The thickness of the surface layer is suitably set depending upon the particular application. For example, in the case of a surface layer to be formed on a DLC film of a magnetic disk, the thickness is preferably from 0.1 to 2 nm, particularly preferably from 0.5 to 1 nm. When the thickness of the surface layer is at least the lower limit value in the above range, the lubricating effects, etc. by the surface layer can be obtained sufficiently. When it is at most the upper limit value within the above range, such can highly contribute to high density recording of the magnetic recording medium.

According to the fluorinated ether composition of the present invention, it is possible to form a surface layer which exhibits sufficient lubricity even when its thickness is made thin. Therefore, the thinner the thickness of the surface layer, the higher the usefulness of the present invention.

The thickness of the surface layer may, for example, be calculated from the oscillation period of interference patterns of reflected X-rays obtained by X-ray reflectivity technique by means of an X-ray diffraction meter for thin film analysis ATX-G (manufactured by RIGAKU CORPORATION).

A liquid composition may be prepared by adding a liquid medium to the fluorinated ether composition of the present invention. Particularly, in a case where the fluorinated ether composition of the present invention is to be used as a surface modifier in an application to form a surface layer on a substrate, it is preferred to use it as a liquid composition by adding a liquid medium to the fluorinated ether composition of the present invention.

[Surface Modifier or Surfactant]

The surface modifier or surfactant (which may collectively be referred to also as “the surface modifier or the like”) of the present invention is one containing the fluorinated ether composition of the present invention.

The surface modifier or the like of the present invention may be one which is composed solely of the fluorinated ether composition of the present invention, or one which may further contain other components.

The content of the fluorinated ether composition of the present invention in the surface modifier or the like of the present invention, is preferably from 90 to 100 mass %, particularly preferably 100 mass %, to the total mass of the surface modifier or the like. That is, the surface modifier or the like of the present invention is particularly preferably composed of the fluorinated ether composition of the present invention.

As other components which may be contained, optional compounds which are useful as surface modifiers or surfactants and which do not correspond to the fluorinated ether compounds, may be used, and, for example, coupling agents of silane type, epoxy type, titanium type, aluminum type, etc. may be mentioned. In a case where the fluorinated ether composition of the present invention is to be used as a surface modifier, by using such a coupling agent, it is possible to improve the adhesion between the substrate and the compound (A).

The surface modifier may be used in an application as a lubricant. Further, it may be used as applied on a film or sheet made of a resin, in an application to control the refractive index of the resin, or in an application to improve the chemical resistance of the resin.

As the lubricant, it is preferably used for a magnetic disk, particularly in an application to impart lubricity as applied on a diamond-like carbon protective film (DLC film) of a magnetic disk.

As the surfactant, it may, for example, be used as an additive or leveling agent to lower the surface tension of a coating material, or as a leveling agent for a polishing liquid. When added to a coating material, it is preferably added so that the amount of the fluorinated ether composition of the present invention will be at a level of from 0.01 to 5 mass % to the coating material.

[Liquid Composition]

The liquid composition of the present invention comprises the fluorinated ether composition of the present invention and a liquid medium.

The liquid composition of the present invention may be any one of a solution, a suspension and an emulsion, and is preferably a solution.

The concentration of the fluorinated ether composition of the present invention in the liquid composition may suitably adjusted depending upon the particular application and is preferably from 0.005 to 50 mass %, more preferably from 0.05 to 5 mass %, particularly preferably from 0.01 to 1 mass %, to the total mass of the liquid composition. When the concentration of the fluorinated ether composition is within the above range, a uniform surface layer can be formed.

The liquid medium may be any medium so long as it is capable of dissolving or dispersing the fluorinated ether composition of the present invention and is preferably an organic solvent. The organic solvent may be a fluorinated organic solvent or a non-fluorinated organic solvent, or may contain both of such solvents.

The fluorinated organic solvent may, for example, be a fluoro-alkane, a fluoro-aromatic compound, a fluoro-alkyl ether, a fluoro-alkylamine, or a fluoro-alcohol.

The fluoro-alkane is preferably a C₄₋₈ compound. As commercial products, for example, C₆F₁₃H (trade name: AC-2000, manufactured by Asahi Glass Co., Ltd.), C₆F₁₃C₂H₅ (trade name: AC-6000, manufactured by Asahi Glass Co., Ltd.), C₂F₅CHFCHFCF₃ (trade name: Vertrel-XF, manufactured by DuPont), etc. may be mentioned.

The fluoro-aromatic compound may, for example, be hexafluorobenzene, trifluoromethylbenzene, perfluorotoluene, or bis(trifluoromethyl)benzene.

The fluoro-alkyl ether is preferably a C₄₋₁₂ compound. As the fluoro-alkyl ether, a hydrofluoroalkyl ether is preferred. As commercial products, for example, CF₃CH₂OCF₂CF₂H (trade name: AE-3000, manufactured by Asahi Glass Co., Ltd.), C₄F₉OCH₃ (trade name: Novec-7100, manufactured by 3M), C₄F₉OC₂H₅ (trade name: Novec-7200, manufactured by 3M), C₆F₁₃OCH₃ (trade name: Novec-7300, manufactured by 3M), etc. may be mentioned.

The fluoro-alkylamine is preferably a perfluoro-alkylamine, and, for example, perfluorotripropylamine or perfluorotributylamine may be mentioned.

The fluoro-alcohol may, for example, be 2,2,3,3-tetrafluoropropanol, 2,2,2-trifluoroethanol or hexafluoroisopropanol.

From the viewpoint of the solubility of the fluorinated ether compounds, the fluorinated organic solvent is preferably a fluoro-alkane, a fluoro-aromatic compound, or a fluoro-alkyl ether. Among them, particularly preferred is a hydrofluoro-alkyl ether in that the ozone depletion potential is low.

The non-fluorinated organic solvent is preferably a compound composed solely of hydrogen atoms and carbon atoms, or a compound composed solely of hydrogen atoms, carbon atoms and oxygen atoms, and may, for example, be a hydrocarbon type organic solvent, an alcohol type organic solvent, a ketone type organic solvent, an ether type organic solvent or an ester type organic solvent.

The hydrocarbon type organic solvent is preferably e.g. hexane, heptane or cyclohexane.

The alcohol type organic solvent is preferably e.g. methanol, ethanol, propanol or isopropanol.

The ketone type organic solvent is preferably e.g. acetone, methyl ethyl ketone, or methyl isobutyl ketone.

The ether type organic solvent is preferably e.g. diethyl ether, tetrahydrofuran, or tetraethylene glycol dimethyl ether.

The ester type organic solvent is preferably e.g. ethyl acetate or butyl acetate.

From the viewpoint of the solubility of the fluorinated ether compounds, the non-fluorinated organic solvent is particularly preferably a ketone type organic solvent.

The liquid medium is preferably at least one organic solvent selected from the group consisting of a fluoro-alkane, a fluoro-aromatic compound, a fluoro-alkyl ether, a compound composed solely of hydrogen atoms and carbon atoms, and a compound composed solely of hydrogen atoms, carbon atoms and oxygen atoms. Particularly preferred is a fluorinated organic solvent selected from a fluoro-alkane, a fluoro-aromatic compound and a fluoro-alkyl ether.

With a view to increasing the solubility of the fluorinated ether compounds, the liquid medium preferably contains at least one organic solvent selected from the group consisting of, as fluorinated organic solvents, a fluoro-alkane, a fluoro-aromatic compound and a fluoro-alkyl ether, and, as a non-fluorinated organic solvent, a compound composed solely of hydrogen atoms, carbon atoms and oxygen atoms, in an amount in total of at least 90 mass % of the entire liquid medium.

As the case requires, the liquid composition may further contain other components in addition to the fluorinated ether composition of the present invention and the solvent, within a range not to impair the effects of the present invention.

In a case where the fluorinated ether composition of the present invention is used as a lubricant, a radical scavenger (e.g. trade name: X-1p, manufactured by Dow Chemicals), etc. may be mentioned as such other components.

The liquid composition should preferably not contain metal ions, anions, moisture, low molecular weight polar compounds, etc., since, otherwise, the desired performance may not be attained.

Metal ions (such as Na, K, Ca, Al, etc.) are likely to be bonded to anions to form a Lewis acid catalyst and thereby to accelerate a decomposition reaction of the fluorinated ether compounds. Anions (such as F, Cl, NO₂, NO₃, PO₄, SO₄, C₂O₄, etc.) and moisture are likely to corrode the surface of a substrate. Accordingly, the moisture content in the liquid composition is preferably at most 2,000 ppm. Low molecular weight polar compounds (such as alcohols, plasticizers eluting from resins, etc.) are likely to lower the adhesion between the substrate and the surface layer.

As the method of using the liquid composition, a known method may be employed depending upon the particular purpose.

For example, in a case where the fluorinated ether composition of the present invention is to be used as a surface modifier, it is preferred that the liquid composition containing the fluorinated ether composition of the present invention is applied on a substrate and dried to form a coating film (surface layer) containing the fluorinated ether composition of the present invention, thereby to have the desired function exhibited.

The substrate on which the liquid composition of the present invention is to be applied, is not particularly limited and may, for example, be the same one as mentioned above as the substrate on which the surface layer is to be formed. From the viewpoint of usefulness of the present invention, a magnetic disk is preferred as the substrate.

The coating method for the liquid composition may, for example, be a roll coating method, a casting method, a dip coating method, a spin coating method, a casting-on-water method, a die coating method, a Langmuir-Blodgett method, or a vacuum vapor deposition method, and is preferably a pin coating method, a dip coating method or a vacuum vapor deposition method.

The drying method may, for example, be natural drying, vacuum drying, centrifugal drying or heat drying.

After forming the surface layer by applying the liquid composition on the substrate, adhesion treatment may be carried out in order to firmly bond the fluorinated ether composition on the substrate (e.g. on a carbon protective film of a magnetic disk).

Such adhesion treatment may, for example, be heat treatment, ultraviolet irradiation treatment or plasma treatment, and is preferably heat treatment or ultraviolet irradiation treatment, particularly preferably heat treatment. Drying treatment may serve also as adhesion treatment.

Further, the substrate after the adhesion treatment, may be cleaned by a fluorinated organic solvent for the purpose of removing fouling or removing excess fluorinated ether compounds.

(Article)

The article of the present invention is one having a film made of the fluorinated ether composition of the present invention, on a substrate.

The substrate on which the liquid composition of the present invention is to be applied, is not particularly limited and may, for example, be the same one as mentioned above as the substrate on which the surface layer is to be formed. From the viewpoint of usefulness of the present invention, a magnetic disk is preferred as the substrate.

As the method for forming such a film on the substrate, a method known as a method for forming a film made of a fluorinated ether composition may be employed. For example, such a film may be formed by e.g. the above mentioned method for forming a surface layer by applying the liquid composition of the present invention on a substrate.

EXAMPLES

Now, the present invention will be described in detail with reference to Examples. However, it should be understood that the present invention is by no means restricted by these Examples. Here, Ex. 1, Ex. 5 and Ex. 6 are Examples of the present invention, and Ex. 2 to 4 are Comparative Examples.

Evaluation methods used in each Ex. are as follows.

[Evaluation Methods] (GPC Analysis)

The number average molecular weight (Mn) and the molecular weight distribution (Mw/Mn) were measured by gel permeation chromatography (hereinafter referred to also as “GPC”). Here, Mw is meant for a mass average molecular weight.

The measurement by GPC was in accordance with the method disclosed in JP-A-2001-208736 and was conducted under the following conditions.

Mobile phase: A mixed solvent of R-225 (Asahiklin AK-225SEC Grade 1, manufactured by Asahi Glass Co., Ltd.) and hexafluoroisopropyl alcohol (R-225:hexafluoroisopropyl alcohol=99:1 (volume ratio))

Analytical column: One having two PLgel MIXED-E columns (manufactured by Polymer Laboratories) connected in series.

Standard samples for measuring molecular weight: Four types of perfluoropolyether having Mw/Mn of less than 1.1 and Mn of from 2,000 to 10,000, and one type of perfluoropolyether having Mw/Mn of at least 1.1 and Mn of 1,300

Flow rate of mobile phase: 1.0 mL/min.

Column temperature: 37° C.

Detector: evaporative light scattering detector

(NMR Analyses)

The NMR analyses were conducted under the following conditions.

As the standard substance for ¹H-NMR (300, 4 MHz), nitrobenzene was used at 7.5 ppm.

As the standard substance for ¹⁹F-NMR (282, 7 MHz), perfluorobenzene was used at −162.5 ppm.

As the solvent for NMR, R-113 (CCl₂FCClF₂) was used, unless otherwise specified.

(Measurement of Dynamic Friction Coefficient)

The dynamic friction coefficient of the outermost surface (among surfaces of an article, a place where a surface layer was formed) of an article having a surface layer formed on a substrate, was measured by means of a friction measurement device (Tribogear, manufactured by Heidon). As the contractor, a SUS ball having a diameter of 10 mm was used, and the measurement was made under a load of 100 g at a moving distance of 20 mm at a moving speed of 1 mm/sec.

(Measurement of F/Si)

The coverage factor of the surface layer formed on a substrate (silicon wafer) was evaluated by F/Si measured under the following measurement conditions by an X-ray Photoelectron Spectroscopy (XPS).

XPS is a method wherein characteristic X-rays of e.g. Al or Mg are applied to a sample, and the kinetic energy and intensity of photoelectrons emitted by photoelectric effects are measured, to know the types, amounts, chemical bonding states, etc. of atoms present at the solid surface.

The kinetic energy Ek of photoelectrons emitted from the sample is a value (Ek=hv−Eb−W) obtained by subtracting the bonding energy Eb and the work function W from the incident X-ray energy hv (h: Planck's constant, v: vibration frequency). The bonding energy Eb is a value depending on the types, electron orbitals and chemical bonding states of atoms by which photoelectrons were protected in the sample. The incident X-ray energy hv and the work function W are already known. Therefore, if the kinetic energy Ek is measured, the bonding energy Eb can be obtained, and it is possible to know the types, electron orbitals and chemical bonding states of atoms in the sample.

The incident X-rays will penetrate at a depth of a few μm into the sample. However, electrons emitted from atoms present at a deep location tend to lose energy by e.g. inelastic scattering with electrons constrained by other atoms in the sample and thus will not be emitted from the sample. Therefore, electrons emitted from the outermost surface at a depth of a few nm, determined by the inelastic mean free path (the distance where electrons can go forward without undergoing inelastic scattering), are observed as photoelectrons. Thus, XPS is a method for measuring, at a high sensitivity, the type, amounts and chemical bonding states of atoms present at the outermost surface of the sample, whereby an extremely thin film applied on a substrate can be detected at a high sensitivity, and thus is a method effective for evaluating the coverage factor of a thin film.

When the outermost surface of an article obtained in each Ex. given hereinafter (i.e. an article wherein a silicon water is used as a substrate, and a surface layer made of a surface modifier containing fluorinated ether compounds, is formed on the substrate) is subjected to the XPS measurement, at a portion covered with the surface layer on the substrate, the intensity of photoelectrons emitted from the 1s orbital of fluorine atoms in the surface layer (hereinafter referred to as F1s peak intensity) will be strongly detected, and the intensity of photoelectrons emitted from the Si2p orbital of silicon atoms in the substrate (hereinafter referred to as Si2p peak intensity) will be weakly detected or will not be detected. Whereas, at a portion not covered with the surface layer on the substrate, photoelectrons emitted from fluorine atoms will not be detected, and the intensity of photoelectrons emitted from the Si2p orbital of silicon atoms will be strongly detected. Accordingly, the ratio of the F atom concentration and the Si atom concentration calculated, respectively, from the F1s peak intensity and the Si2p peak intensity obtained by the XPS measurement, is considered to be in a positive correlation with the coverage factor of the surface layer formed on the substrate.

<Conditions for XPS Measurement>

As the XPS apparatus, PHI Quantera SXM manufactured by ULVAC-PHI, Inc., was used. Using, as an X-ray source, AlK_(α) ray (1486.6 eV) focused to a diameter of about 50 μm, the measurement was conducted at an irradiated X-ray intensity of 12.4 W, with a pass energy of the detector being 224 eV and at a photoelectron-takeoff angle of 45°. The measurement was conducted by fixing the irradiated X-ray without scanning, and the outermost surface of the sample was measured, and no etching of the sample was conducted. For a charge correction along with emission of photoelectrons from the sample, an electron beam and an Ar+ neutralizing gun provided as an accessory to the apparatus were used. An integrated intensity of peaks having the background removed, was used within an energy range of the bonding energy of from 682 to 691 eV in the calculation of the F1s peak intensity, and within an energy range of the bonding energy of from 96 to 107 eV in the calculation of the Si2p peak intensity. Further, using relative sensitivity coefficients of the respective elements specific to the apparatus, the F atom concentration and the Si atom concentration were calculated.

Preparation Example 1 Preparation of Fluorinated Ether Compound (A)

The following compound (A6-1) was prepared by the following procedure.

To dipentaerythritol, ethylene oxide was added by a known method to obtain an ethylene oxide adduct.

The ethylene oxide adduct was reacted with FCOCF(CF₃)OCF₂CF(CF₃)O(CF₂)₃F (hereinafter referred to also as “RfF”) to obtain an esterified derivative.

The esterified derivative (30 g) was dissolved in R-113 (270 g) and fluorinated by using fluorine gas diluted to 20% with nitrogen gas (hereinafter referred to also as “20% fluorine gas”). From the product, the solvent was distilled off under reduced pressure to obtain a fluorinated derivative which was liquid at room temperature.

To the fluorinated derivative, 1,1,3,4-tetrachlorohexafluorobutane and KF were added and vigorously stirred, and a hydrolysis reaction was conducted at 120° C. to obtain a hydrolyzed product which was liquid at room temperature.

To the hydrolyzed product, KF and R-113 were put, and ethanol was added, followed by a reaction for 8 hours while maintaining the temperature not to become lower than 25° C., whereupon an ethyl ester derivative was obtained by removing KF, R-113 and ethanol.

To the ethyl ester derivative, R-225 and tetrahydrofuran (200 mL) were mixed, and a borane-tetrahydrofuran complex was added in a nitrogen stream, followed by a reaction over night at room temperature (reduction reaction). Then, the solvent was distilled off by an evaporator, and to the residue, 2 mol/L of hydrochloric acid was added, followed by extraction with R-225. The extract was concentrated to obtain a crude product (59.71 g).

The obtained crude product was purified by silica gel column (the method disclosed in Examples in JP-A-2009-197210) and then, subjected to supercritical purification (the method disclosed in Examples in JP-A-2009-197210).

With respect to the obtained purified product (compound (A6-1)), NMR analyses (¹H-NMR and ¹⁹F NMR) and GPC analysis were carried out. The results of the NMR analyses are shown below. The purified product had Mn of 5,867 (average value of b1 to b6: 7.1) and Mw/Mn of 1.10.

¹H-NMR δ(ppm): 3.94

¹⁹F-NMR δ(ppm): −80.1, −88.2 to −90.5, −135.0 to −139.0

Preparation Example 2 Preparation of Fluorinated Ether Compound (B)

The following compound (B4-1) was prepared by the following procedure.

Diglycerin-initiated polyoxyethylene tetraol (“diglycerin-initiated polyoxyethylene glyceryl ether SC-E1500” manufactured by Sakamoto Yakuhin Kogyo Co., Ltd.) was reacted with RfF to obtain an esterified derivative.

The esterified derivative (30 g) was dissolved in R-113 (270 g) and fluorinated by using 20% fluorine gas. From the product, the solvent was distilled off under reduced pressure to obtain a fluorinated derivative which was liquid at room temperature.

To the fluorinated derivative, 1,1,3,4-tetrachlorohexafluorobutane and KF were added and vigorously stirred, and a hydrolysis reaction was conducted at 120° C. to obtain a hydrolyzed product which was liquid at room temperature.

To the hydrolyzed product, KF and R-113 were put, and ethanol was added, followed by a reaction for 8 hours while maintaining the temperature not to become lower than 25° C., whereupon an ethyl ester derivative was obtained by removing KF, R-113 and ethanol.

To the ethyl ester derivative, R-225 and tetrahydrofuran (200 mL) were mixed, and a borane-tetrahydrofuran complex was added in a nitrogen stream, followed by a reaction over night at room temperature (reduction reaction). Then, the solvent was distilled off by an evaporator, and to the residue, 2 mol/L of hydrochloric acid was added, followed by extraction with R-225. The extract was concentrated to obtain a crude product (51.58 g).

The obtained crude product was purified by silica gel column (the method disclosed in Examples in JP-A-2009-197210) and then, subjected to supercritical purification (the method disclosed in Examples in JP-A-2009-197210).

With respect to the obtained purified product (compound (B4-1)), NMR analyses (¹H-NMR and ¹⁹F NMR) and GPC analysis were carried out. The results of the NMR analyses are shown below. The purified product had Mn of 2,593 (average value of b7 to b10: 3.9) and Mw/Mn of 1.07.

¹H-NMR δ(ppm): 3.94

¹⁹F-NMR δ(ppm): −80.1, −88.2 to −90.5, −135.0 to −139.0

Ex. 1 Production of Fluorinated Ether Composition 1

Compound (A6-1) obtained in Preparation Example 1 and compound (B4-1) obtained in Preparation Example 2 were mixed in a mass ratio of (A6-1):(B4-1)=55:45 and thoroughly stirred to produce a fluorinated ether composition 1.

(Production of Liquid Composition 1)

The fluorinated ether composition 1 was dissolved in Vertrel-XF (manufactured by DuPont) so that the concentration would be 0.05 mass %, to produce a liquid composition 1.

(Production of Article 1)

The liquid composition 1 was applied to a silicon wafer by dip coating to obtain an article (surface layer-equipped substrate) 1. Using as the dip coater, Microspeed Dip Coater, manufactured by SDI Co., Ltd., the silicon wafer was dipped at a dipping speed of 10 mm/sec. and after dipping for 60 seconds, withdrawn at a speed of 2 mm/sec. The withdrawn silicon wafer was heated in an oven at 150° C. for 10 minutes to form a surface layer, whereby the article 1 was obtained.

(Evaluation)

With respect to the article 1, the dynamic friction coefficient and F/Si of the outermost surface (the place having the surface layer formed among surfaces of the article) were measured. The results are shown in Table 1. Further, the outermost surface composition (atm %) of the article 1 measured by XPS is shown in Table 2.

Ex. 2 to 6

Fluorinated ether compositions 2 to 6 were obtained in the same manner as in Ex. 1 except that the mass ratio of compound (A6-1) and compound (B4-1) was changed to the values as shown in Table 1.

Liquid compositions 2 to 6 were prepared in the same manner as in Ex. 1 except that the fluorinated ether compositions 2 to 6 were used instead of the fluorinated ether composition 1, and using them, articles 2 to 6 were obtained. With respect to the articles 2 to 4, dynamic friction coefficients and F/Si were measured. The results are shown in Table 1. Further, the outermost surface compositions (atm %) of the articles 2 to 4 measured by XPS are shown in Table 2.

TABLE 1 Ex. Ex. Ex. Ex. Ex. Ex. 1 2 3 4 5 6 Fluorinated Compound (A) 55 10 85 98 45 70 ether Compound (B) 45 90 15 2 55 30 composition (mass %) Evaluations Dynamic 0.14 0.15 0.19 0.19 0.12 0.12 friction coefficient F/Si 0.86 0.34 2.0 2.8 2.0 2.3

TABLE 2 Outermost surface composition (atm %) C O F Si Ex. 1 14.6 30.1 25.6 29.7 Ex. 2 4.7 37.9 14.5 42.9 Ex. 3 18.8 24.4 38.1 18.7 Ex. 4 19.9 22.4 42.5 15.2

In the article 1 obtained in Ex. 1, the dynamic friction coefficient of the outermost surface was low, and the surface layer had high lubricity. Further, in the article 1, the outermost surface composition had a F atom concentration of 25.6 atm % and a Si atom concentration of 29.7 atm %, whereby the value of F/Si was significantly high as compared with in Ex. 2, and the coverage factor of the substrate surface by the surface layer was high. As the coverage factor was high, it was confirmed that the amount of the fluorinated ether composition 1 attached to the substrate surface was sufficient, and the adhesion to the substrate was excellent. From these results, it was confirmed that according to the fluorinated ether composition 1, it is possible to develop excellent lubricity and adhesion.

On the other hand, in the article 2 in Ex. 2 obtained by using the fluorinated ether composition 2 wherein the content of the compound (A) was 10 mass %, while the lubricity of the surface layer was high, the value of F/Si was small, the amount of the fluorinated ether composition 2 attached to the substrate surface was small, and the adhesion was poor.

In the articles 3 and 4 in Ex. 3 and 4 obtained by using the fluorinated ether compositions 3 and 4 wherein the contents of the compound (A) as a fluorinated ether compound were 85 and 98 mass %, respectively, while the value of F/Si was large, the dynamic friction coefficient was large, and the lubricity of the surface layer was insufficient.

Further, in the articles 5 and 6 in Ex. 5 and 6 obtained by using the fluorinated ether compositions 5 and 6 wherein the contents of the compound (A) as a fluorinated ether compound were 45 and 70 mass %, respectively, while the value of F/Si is large (about the same as in the articles 3 and 4) as compared with the articles 1 and 2, the dynamic friction coefficient is further smaller than the article 1, whereby the fluorinated ether compositions 5 and 6 are particularly suitable for applications wherein high lubricity is required.

INDUSTRIAL APPLICABILITY

The fluorinated ether composition of the present invention is useful as a surface modifier or a surfactant and is particularly useful as a lubricant for a magnetic recording medium such as a hard disk.

This application is a continuation of PCT Application No. PCT/JP2014/053206, filed on Feb. 12, 2014, which is based upon and claims the benefit of priority from Japanese Patent Application No. 2013-025906 filed on Feb. 13, 2013. The contents of those applications are incorporated herein by reference in their entireties. 

What is claimed is:
 1. A fluorinated ether composition comprising a fluorinated ether compound (A) represented by the following formula (A) and a fluorinated ether compound (B) represented by the following formula (B), wherein the content of the fluorinated ether compound (A) is from 15 to 80 mass % to the total amount of the fluorinated ether compound (A) and the fluorinated ether compound (B): (X)_(n)—Y^(A)—(Z)_(m)  (A) (X)_(s)—Y^(B)—(Z)_(t)  (B) provided that the symbols in the formulae have the following meanings: in the above formula (A), X is a group represented by the following formula (X), Z is a group represented by the following formula (Z), n is 5 or 6, m is an integer of from 0 to 10, n+m is an integer of from 5 to 16, and Y^(A) is a (n+m) valent linking group, and in the above formula (B), X and Z have the same meanings as above, respectively, s is an integer of from 0 to 4, t is an integer of from 0 to 10, s+t is an integer of from 2 to 14, and Y^(B) is a (s+t) valent linking group: HO—CH₂—P¹-[(C_(a)F_(2a)O)_(b)(CFQ¹CF₂O)_(c)]—  (X) R—P²-[(C_(d)F_(2d)O)_(e)(CFQ²CF₂O)_(f)]—  (Z) in the above formula (X), a is an integer of from 1 to 5, b is an integer of from 1 to 100, c is an integer of from 0 to 100, P¹ is a bivalent linking group containing neither hydroxy group nor alkoxy group, or a single bond, and Q¹ is a halogen atom other than a fluorine atom, a hydrogen atom, a monovalent hydrocarbon group, a fluoroalkyl group, or a fluoroalkyl group having an etheric oxygen atom inserted between carbon-carbon atoms, provided that when b is 2 or more, the plurality of a corresponding to b present in the same molecule may be the same or different from one another, when c is 2 or more, the plurality of Q¹ corresponding to c present in the same molecule may be the same or different from one another, and alignment sequence of b number of (C_(a)F_(2a)O) units and c number of (CFQ¹CF₂O) units in a molecule may be any sequence, in the above formula (Z), d is an integer of from 1 to 5, e is an integer of from 1 to 100, f is an integer of from 0 to 100, P² is a bivalent linking group containing neither hydroxyl group nor alkoxy group, or a single bond, Q² is a halogen atom other than a fluorine atom, a hydrogen atom, a monovalent hydrocarbon group, a fluoroalkyl group, or a fluoroalkyl group having an etheric oxygen atom inserted between carbon-carbon atoms, and R is a hydrogen atom, a halogen atom, a monovalent hydrocarbon group, a fluoroalkyl group, or a fluoroalkyl group having an etheric oxygen atom inserted between carbon-carbon atoms, provided that when e is 2 or more, the plurality of d corresponding to e present in the same molecule may be the same or different from one another, when f is 2 or more, the plurality of Q² corresponding to f present in the same molecule may be the same or different from one another, and alignment sequence of e number of (C_(d)F_(2d)O) units and f number of (CFQ²CF₂O) units in a molecule may be any sequence.
 2. The fluorinated ether composition according to claim 1, wherein the number average molecular weight in total of the fluorinated ether compound (A) and the fluorinated ether compound (B) is from 500 to 50,000.
 3. The fluorinated ether composition according to claim 1, wherein the fluorinated ether compound (A) has a number average molecular weight of from 2,000 to 50,000 and a molecular weight distribution (Mw/Mn) of from 1.00 to 1.65.
 4. The fluorinated ether composition according to claim 1, wherein the fluorinated ether compound (B) has a number average molecular weight of from 500 to 10,000 and a molecular weight distribution (Mw/Mn) of from 1.00 to 1.65.
 5. The fluorinated ether composition according to claim 1, wherein the fluorinated ether compound (A) is a compound of the above formula (A) wherein m is an integer of from 0 to 3, X is a group represented by the following formula (X-1), and Z is a group represented by the following formula (Z-1): HO—CH₂—CF₂O—(CF₂CF₂O)_(b-1)—  (X-1) R—O—(CF₂CF₂O)_(e)—  (Z-1) provided that the symbols in the formulae have the following meanings: in the above formula (X-1), b is an integer of from 1 to 100, in the above formula (Z-1), e is an integer of from 1 to 100, and R is as defined above.
 6. The fluorinated ether composition according to claim 5, wherein the above Y^(A) is a perfluoro organic group obtained by perfluorinating a group with a structure having hydroxy groups removed from a penta- or hexa-polyhydric alcohol.
 7. The fluorinated ether composition according to claim 1, wherein the fluorinated ether compound (B) is a compound of the above formula (B) wherein s is 4, t is from 0 to 2, X is a group represented by the following formula (X-1), and Z is a group represented by the following formula (Z-1): HO—CH₂—CF₂O—(CF₂CF₂O)_(b-1)—  (X-1) R—O—(CF₂CF₂O)_(e)—  (Z-1) provided that the symbols in the formulae have the following meanings: in the above formula (X-1), b is an integer of from 1 to 100, in the above formula (Z-1), e is an integer of from 1 to 100, and R is as defined above.
 8. The fluorinated ether composition according to claim 7, wherein the above Y^(B) is a perfluoro organic group obtained by perfluorinating a group with a structure having hydroxy groups removed from a tetra- to hexa-polyhydric alcohol.
 9. A surface modifier or surfactant containing the fluorinated ether composition as defined in claim
 1. 10. A lubricant for a magnetic recording medium, containing the fluorinated ether composition as defined in claim
 1. 11. A liquid composition comprising the fluorinated ether composition as defined in claim 1 and a liquid medium.
 12. The liquid composition according to claim 11, wherein the concentration of the fluorinated ether composition is from 0.005 to 50 mass %.
 13. The liquid composition according to claim 11, wherein the liquid medium is a fluorinated organic solvent selected from a fluoro-alkane, a fluoro-aromatic compound and a fluoro-alkyl ether.
 14. A coating method which comprises applying the liquid composition as defined in claim 11 to a substrate surface and then, removing the liquid medium to form a film made of the fluorinated ether composition on the substrate surface.
 15. An article having a film made of the fluorinated ether composition as defined in claim 1, on a substrate. 